KVM/ARM Fixes for v4.11-rc6

Fixes include:
  - Fix a problem with GICv3 userspace save/restore
  - Clarify GICv2 userspace save/restore ABI
  - Be more careful in clearing GIC LRs
  - Add missing synchronization primitive to our MMU handling code
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Merge tag 'kvm-arm-for-v4.11-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm

From: Christoffer Dall <cdall@linaro.org>

KVM/ARM Fixes for v4.11-rc6

Fixes include:
 - Fix a problem with GICv3 userspace save/restore
 - Clarify GICv2 userspace save/restore ABI
 - Be more careful in clearing GIC LRs
 - Add missing synchronization primitive to our MMU handling code

Documentation/virtual/kvm/devices/arm-vgic.txt

@@ -83,6 +83,12 @@ Groups:
 
     Bits for undefined preemption levels are RAZ/WI.
 
+    For historical reasons and to provide ABI compatibility with userspace we
+    export the GICC_PMR register in the format of the GICH_VMCR.VMPriMask
+    field in the lower 5 bits of a word, meaning that userspace must always
+    use the lower 5 bits to communicate with the KVM device and must shift the
+    value left by 3 places to obtain the actual priority mask level.
+
   Limitations:
     - Priorities are not implemented, and registers are RAZ/WI
     - Currently only implemented for KVM_DEV_TYPE_ARM_VGIC_V2.

arch/arm/kvm/arm.c

@@ -1124,6 +1124,9 @@ static void cpu_hyp_reinit(void)
 		if (__hyp_get_vectors() == hyp_default_vectors)
 			cpu_init_hyp_mode(NULL);
 	}
+
+	if (vgic_present)
+		kvm_vgic_init_cpu_hardware();
 }
 
 static void cpu_hyp_reset(void)

arch/arm/kvm/mmu.c

@@ -292,11 +292,18 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
 	phys_addr_t addr = start, end = start + size;
 	phys_addr_t next;
 
+	assert_spin_locked(&kvm->mmu_lock);
 	pgd = kvm->arch.pgd + stage2_pgd_index(addr);
 	do {
 		next = stage2_pgd_addr_end(addr, end);
 		if (!stage2_pgd_none(*pgd))
 			unmap_stage2_puds(kvm, pgd, addr, next);
+		/*
+		 * If the range is too large, release the kvm->mmu_lock
+		 * to prevent starvation and lockup detector warnings.
+		 */
+		if (next != end)
+			cond_resched_lock(&kvm->mmu_lock);
 	} while (pgd++, addr = next, addr != end);
 }
 
@@ -803,6 +810,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 	int idx;
 
 	idx = srcu_read_lock(&kvm->srcu);
+	down_read(&current->mm->mmap_sem);
 	spin_lock(&kvm->mmu_lock);
 
 	slots = kvm_memslots(kvm);
@@ -810,6 +818,7 @@ void stage2_unmap_vm(struct kvm *kvm)
 		stage2_unmap_memslot(kvm, memslot);
 
 	spin_unlock(&kvm->mmu_lock);
+	up_read(&current->mm->mmap_sem);
 	srcu_read_unlock(&kvm->srcu, idx);
 }
 
@@ -829,7 +838,10 @@ void kvm_free_stage2_pgd(struct kvm *kvm)
 	if (kvm->arch.pgd == NULL)
 		return;
 
+	spin_lock(&kvm->mmu_lock);
 	unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE);
+	spin_unlock(&kvm->mmu_lock);
+
 	/* Free the HW pgd, one page at a time */
 	free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE);
 	kvm->arch.pgd = NULL;
@@ -1801,6 +1813,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	    (KVM_PHYS_SIZE >> PAGE_SHIFT))
 		return -EFAULT;
 
+	down_read(&current->mm->mmap_sem);
 	/*
 	 * A memory region could potentially cover multiple VMAs, and any holes
 	 * between them, so iterate over all of them to find out if we can map
@@ -1844,8 +1857,10 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 			pa += vm_start - vma->vm_start;
 
 			/* IO region dirty page logging not allowed */
-			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES)
+			if (memslot->flags & KVM_MEM_LOG_DIRTY_PAGES) {
-				return -EINVAL;
+				ret = -EINVAL;
+				goto out;
+			}
 
 			ret = kvm_phys_addr_ioremap(kvm, gpa, pa,
 						    vm_end - vm_start,
@@ -1857,7 +1872,7 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	} while (hva < reg_end);
 
 	if (change == KVM_MR_FLAGS_ONLY)
-		return ret;
+		goto out;
 
 	spin_lock(&kvm->mmu_lock);
 	if (ret)
@@ -1865,6 +1880,8 @@ int kvm_arch_prepare_memory_region(struct kvm *kvm,
 	else
 		stage2_flush_memslot(kvm, memslot);
 	spin_unlock(&kvm->mmu_lock);
+out:
+	up_read(&current->mm->mmap_sem);
 	return ret;
 }
 

include/kvm/arm_vgic.h

@@ -295,6 +295,7 @@ void kvm_vgic_vcpu_early_init(struct kvm_vcpu *vcpu);
 void kvm_vgic_vcpu_destroy(struct kvm_vcpu *vcpu);
 int kvm_vgic_map_resources(struct kvm *kvm);
 int kvm_vgic_hyp_init(void);
+void kvm_vgic_init_cpu_hardware(void);
 
 int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int intid,
 			bool level);

include/linux/irqchip/arm-gic.h

@@ -96,6 +96,9 @@
 #define GICH_MISR_EOI			(1 << 0)
 #define GICH_MISR_U			(1 << 1)
 
+#define GICV_PMR_PRIORITY_SHIFT		3
+#define GICV_PMR_PRIORITY_MASK		(0x1f << GICV_PMR_PRIORITY_SHIFT)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/irqdomain.h>

virt/kvm/arm/vgic/vgic-init.c

@@ -391,6 +391,25 @@ static irqreturn_t vgic_maintenance_handler(int irq, void *data)
 	return IRQ_HANDLED;
 }
 
+/**
+ * kvm_vgic_init_cpu_hardware - initialize the GIC VE hardware
+ *
+ * For a specific CPU, initialize the GIC VE hardware.
+ */
+void kvm_vgic_init_cpu_hardware(void)
+{
+	BUG_ON(preemptible());
+
+	/*
+	 * We want to make sure the list registers start out clear so that we
+	 * only have the program the used registers.
+	 */
+	if (kvm_vgic_global_state.type == VGIC_V2)
+		vgic_v2_init_lrs();
+	else
+		kvm_call_hyp(__vgic_v3_init_lrs);
+}
+
 /**
  * kvm_vgic_hyp_init: populates the kvm_vgic_global_state variable
  * according to the host GIC model. Accordingly calls either

virt/kvm/arm/vgic/vgic-mmio-v2.c

@@ -229,7 +229,15 @@ static unsigned long vgic_mmio_read_vcpuif(struct kvm_vcpu *vcpu,
 		val = vmcr.ctlr;
 		break;
 	case GIC_CPU_PRIMASK:
-		val = vmcr.pmr;
+		/*
+		 * Our KVM_DEV_TYPE_ARM_VGIC_V2 device ABI exports the
+		 * the PMR field as GICH_VMCR.VMPriMask rather than
+		 * GICC_PMR.Priority, so we expose the upper five bits of
+		 * priority mask to userspace using the lower bits in the
+		 * unsigned long.
+		 */
+		val = (vmcr.pmr & GICV_PMR_PRIORITY_MASK) >>
+			GICV_PMR_PRIORITY_SHIFT;
 		break;
 	case GIC_CPU_BINPOINT:
 		val = vmcr.bpr;
@@ -262,7 +270,15 @@ static void vgic_mmio_write_vcpuif(struct kvm_vcpu *vcpu,
 		vmcr.ctlr = val;
 		break;
 	case GIC_CPU_PRIMASK:
-		vmcr.pmr = val;
+		/*
+		 * Our KVM_DEV_TYPE_ARM_VGIC_V2 device ABI exports the
+		 * the PMR field as GICH_VMCR.VMPriMask rather than
+		 * GICC_PMR.Priority, so we expose the upper five bits of
+		 * priority mask to userspace using the lower bits in the
+		 * unsigned long.
+		 */
+		vmcr.pmr = (val << GICV_PMR_PRIORITY_SHIFT) &
+			GICV_PMR_PRIORITY_MASK;
 		break;
 	case GIC_CPU_BINPOINT:
 		vmcr.bpr = val;

virt/kvm/arm/vgic/vgic-v2.c

@@ -36,6 +36,21 @@ static unsigned long *u64_to_bitmask(u64 *val)
 	return (unsigned long *)val;
 }
 
+static inline void vgic_v2_write_lr(int lr, u32 val)
+{
+	void __iomem *base = kvm_vgic_global_state.vctrl_base;
+
+	writel_relaxed(val, base + GICH_LR0 + (lr * 4));
+}
+
+void vgic_v2_init_lrs(void)
+{
+	int i;
+
+	for (i = 0; i < kvm_vgic_global_state.nr_lr; i++)
+		vgic_v2_write_lr(i, 0);
+}
+
 void vgic_v2_process_maintenance(struct kvm_vcpu *vcpu)
 {
 	struct vgic_v2_cpu_if *cpuif = &vcpu->arch.vgic_cpu.vgic_v2;
@@ -191,8 +206,8 @@ void vgic_v2_set_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcrp)
 		GICH_VMCR_ALIAS_BINPOINT_MASK;
 	vmcr |= (vmcrp->bpr << GICH_VMCR_BINPOINT_SHIFT) &
 		GICH_VMCR_BINPOINT_MASK;
-	vmcr |= (vmcrp->pmr << GICH_VMCR_PRIMASK_SHIFT) &
+	vmcr |= ((vmcrp->pmr >> GICV_PMR_PRIORITY_SHIFT) <<
-		GICH_VMCR_PRIMASK_MASK;
+		 GICH_VMCR_PRIMASK_SHIFT) & GICH_VMCR_PRIMASK_MASK;
 
 	vcpu->arch.vgic_cpu.vgic_v2.vgic_vmcr = vmcr;
 }
@@ -207,8 +222,8 @@ void vgic_v2_get_vmcr(struct kvm_vcpu *vcpu, struct vgic_vmcr *vmcrp)
 			GICH_VMCR_ALIAS_BINPOINT_SHIFT;
 	vmcrp->bpr  = (vmcr & GICH_VMCR_BINPOINT_MASK) >>
 			GICH_VMCR_BINPOINT_SHIFT;
-	vmcrp->pmr  = (vmcr & GICH_VMCR_PRIMASK_MASK) >>
+	vmcrp->pmr  = ((vmcr & GICH_VMCR_PRIMASK_MASK) >>
-			GICH_VMCR_PRIMASK_SHIFT;
+			GICH_VMCR_PRIMASK_SHIFT) << GICV_PMR_PRIORITY_SHIFT;
 }
 
 void vgic_v2_enable(struct kvm_vcpu *vcpu)

virt/kvm/arm/vgic/vgic.h

@@ -81,11 +81,18 @@ static inline bool irq_is_pending(struct vgic_irq *irq)
 		return irq->pending_latch || irq->line_level;
 }
 
+/*
+ * This struct provides an intermediate representation of the fields contained
+ * in the GICH_VMCR and ICH_VMCR registers, such that code exporting the GIC
+ * state to userspace can generate either GICv2 or GICv3 CPU interface
+ * registers regardless of the hardware backed GIC used.
+ */
 struct vgic_vmcr {
 	u32	ctlr;
 	u32	abpr;
 	u32	bpr;
-	u32	pmr;
+	u32	pmr;  /* Priority mask field in the GICC_PMR and
+		       * ICC_PMR_EL1 priority field format */
 	/* Below member variable are valid only for GICv3 */
 	u32	grpen0;
 	u32	grpen1;
@@ -130,6 +137,8 @@ int vgic_v2_map_resources(struct kvm *kvm);
 int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
 			     enum vgic_type);
 
+void vgic_v2_init_lrs(void);
+
 static inline void vgic_get_irq_kref(struct vgic_irq *irq)
 {
 	if (irq->intid < VGIC_MIN_LPI)